mic3808 Micrel Semiconductor, mic3808 Datasheet - Page 3

• Manufacturer Part Number: mic3808
• Description: Mic3808/mic3809 Push-pull Pwm Controller
• Manufacturer: Micrel Semiconductor

Pin Description
April 2005
MIC3808/3809
Pin Number
5
6
7
8
Pin Name
OUTB
OUTA
GND
VDD
Pin Function
Ground
Alternating high current output stages. Both stages are capable of driving the
gate of a power MOSFET. Each stage is capable of 500mA peak source
current, and 1A peak sink current. The output stages switch at half the
oscillator frequency, in a push/pull configuration. When the voltage on the
RC pin is rising, one of the two outputs is high, but during fall time, both
outputs are off. This “dead time” between the two outputs, along with a
slower output rise time than fall time, insures that the two outputs can not be
on at the same time. This dead time is typically 60ns to 200ns and depends
upon the values of the timing capacitor and resistor. The high-current output
drivers consist of MOSFET output devices, which switch from V
Each output stage also provides a very low impedance to overshoot and
undershoot. This means that in many cases, external Schottky clamp diodes
are not required.
The power input connection for this device. Although quiescent V
is very low, total supply current will be higher, depending on OUTA and
OUTB current, and the programmed oscillator frequency. Total V
is the sum of quiescent V
the operating frequency and the MOSFET gate charge (Qg), average OUT
current can be calculated from I
prevent noise problems, bypass V
close to the chip as possible. A 1µF decoupling capacitor is recommended.
3
DD
current and the average OUT current. Knowing
OUT
DD
= Qg × F, where F is frequency. To
to GND with a ceramic capacitor as
MIC3808/3809
DD
DD
DD
to GND.
current
current
Micrel